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Like Humans, Mediterranean Sperm Whales Have Their Own Dialects

Much like human languages, the vocalizations of sperm whales evolve over time, as disparate groups of whales develop distinct dialects. A new study shows how an isolated group of sperm whales in the eastern Mediterranean developed its own dialect based on vocalizations used by other whales.

The patterns of clicks issued by sperm whales identify them as part of different "vocal clans." Scientists previously thought that all Mediterranean whales were part of the same clan, which was distinguished by a repeated vocal pattern: three clicks, a short pause, and then a fourth click.

Analyzing 20 years of audio recordings of whales across the Mediterranean, scientists found that sperm whales in the Hellenic Trench, near Greece, produced a faster form of this call than did whales around the Balearic Islands, between Gibraltar and Italy. However, researchers found, the eastern whales would sometimes revert to the older, western dialect. Sperm whales first arrived to the Mediterranean 20,000 years ago, colonizing the sea as they moved from west to east.

"These findings paint a picture of the history of sperm whales living in the Mediterranean, consistent with a progressive occupation from west to east, ending with the development of a distinctive dialect in the animals living in the east," said lead author Taylor Hersh, of the University of Bristol in England. The findings were published in Proceedings of the Royal Society B.

Mediterranean sperm whales are isolated from relatives in other oceans and considered endangered owing to their small numbers and the ongoing threats from fishing and vessel strikes. Estimates put the total number of sperm whales in the Mediterranean below 3,000. Of those, fewer than 300 are found in the Hellenic Trench.

Campaigners have pushed back against oil and gas exploration in the trench, which endangers marine life. To find deposits of fossil fuels, companies undertake seismic surveys, which use sound waves to map the subterranean areas. A recent study found that seismic surveys can damage the hearing of whales and dolphins, induce chronic stress, and potentially lead to strandings.